In recent years, a medical image diagnosis device in which a plurality of medical image diagnosis devices are integrated is being put to practical use. Specifically, a device (referred to also as a PET-CT device) in which a PET (Positron Emission Tomography) diagnosis device for performing function diagnosis with respect to biological tissues of an object and an X-ray CT (Computed Tomography) device for imaging morphological information about biological tissues of an object are integrated is being put to practical use.
This PET-CT device is capable of performing PET examination and X-ray CT examination in succession. Accordingly, the PET-CT device is capable of generating a PET image and an X-ray CT image by one device, and of generating a fused image by combining the PET image and the X-ray CT image.
Now, generally, according to such a medical image diagnosis device, a PET gantry (a radiation detection unit) used by the PET diagnosis device and an X-ray CT gantry (an X-ray scanning unit) used by the X-ray CT device are arranged near each other. Furthermore, such a medical image diagnosis device includes a couch having a top board where an object is to lie, and the PET diagnosis device and the X-ray CT device are to share this couch.
Also, according to such a medical image diagnosis device, the PET gantry of the PET diagnosis device and the X-ray CT gantry of the X-ray CT device are sequentially arranged in tandem, and a tunnel portion is provided inside both gantries in such a way as to pass through the PET gantry and the X-ray CT gantry. The couch has the top board inserted in the tunnel portion inside the gantries along the lengthwise direction of the top board.
Accordingly, with such a medical image diagnosis device, the distance from the couch to the radiation detection unit of the PET diagnosis device and the distance from the couch to the X-ray scanning unit of the X-ray CT device are different, and thus, the sinking of the top board (also referred to as the sagging of the top board) due to the weight is different for each capturing position of the gantries. Accordingly, various methods of correcting the sagging of the top board are being studied.
Now, with a medical image diagnosis, device adopting a plurality of capturing methods, capturing is performed according to each capturing method, and the positions (captured positions) indicated by the captured surfaces are different, and the sagging of the top board is different for each captured position. That is, even with the same captured portion, the sagging of the top board due to weight is different for the PET gantry and for the X-ray CT gantry. Also, since the position of the top board is not shown in a PET image of the PET diagnosis device, alignment of the top boards of the captured images becomes difficult at the time of combining a PET image and an X-ray CT image, and it is difficult to generate a highly accurate fused image where the PET image and the X-ray CT image are appropriately combined.